Lighting devices such as an LED lamp and a lighting apparatus using a light emitting diode as a light source. i.e., a solid-state light emitting device, are commercially available. These devices may consume low electric power and have long life, and they may be used in place of a filament bulb or fluorescent lamp. These lighting apparatuses may include long and narrow straight pipe-shaped lighting apparatuses and LED lamps. The pipe-shaped lighting apparatuses and LED lamps can be used in place of the straight pipe fluorescent lamps widely employed in storage containers such as refrigerators and in indoor and outdoor lighting apparatuses, for example.
However, when the lighting apparatuses and LED lamps are used for illumination in a refrigerator in particular, the use environment is about −25.degree. C. When they are installed outdoors, the temperature is 40.degree. C. or more under burning sun in the summer. In these cases, components constituting these lighting apparatuses, i.e., synthetic resin components and metal components, have different thermal expansion coefficients. For example, in the lighting apparatus made by fixing a light source unit mainly having many metal components having small thermal expansion coefficients onto a transparent tubular cover member made with a synthetic resin having a high thermal expansion coefficient, the thermal expansion coefficient of the cover member is different from the thermal expansion coefficient of the light source unit. For example, when the lighting apparatus is used in an environmental temperature of −25.degree. C., the cover member made of the synthetic resin shrinks more than the light source unit. On the contrary, when the light source unit is placed under burning sun outdoors, the cover member expands more than the light source unit.
The light source unit is affected by stress caused by expansion and shrink of the cover member, and this is one of the causes of malfunction of electronic components including a semiconductor device such as a light emitting diode. Further, when the cover member shrinks, a space is made between components, and this causes the unit to lose air tightness and waterproofing To reduce or avoid these problems components having different thermal expansion coefficients may be carefully configured.